Bolloré is believed to have asked Aegis to request that the UK's Takeover Panel extend an existing "put up or shut up deadline" already imposed on WPP and Hellman and which expires on Friday.

The sources said Aegis is believed to have refused to ask the panel for the extension.

A spokesman for Aegis told Financial News : "We are more than happy to consider viable and realistic bids which will benefit our shareholders. But so far neither WPP nor Hellman & Friedman have put a bid on the table."

WPP was not available for comment and Bolloré declined to comment. Greenhill, the investment bank advising Aegis, was not immediately available for comment.

Bolloré would play a leading role in the three-way bid. He has an estimated £400m (€582.3m) invested in Aegis after building a 25% stake.

Any bid for Aegis in which he is involved would have to be worth at least 143.75p a share, which is the highest price paid for Aegis shares by the French businessman on the market, valuing the UK media space buying group at £1.62bn (€2.3bn), French daily Les Echos reported.